Today there is a strong development going on in automotive industry in order to find systems for decreasing over all fuel consumption. There are many technical areas, which together make up for a good result.
One good way of improving internal combustion engine efficiency is to use some kind of supercharging device to increase intake manifold pressure in order to decrease the internal pumping losses. This in turn leads to decreased fuel consumption. It also makes it possible to downsize the engine without interfering with vehicle performance requirements.
There are several different supercharging devices available but they can all be sorted to one of the following types:                From a vehicle drive shaft, such as for instance a crankshaft, mechanical driven superchargers        Exhaust driven turbo superchargers        Electrical motor driven superchargers        
In some applications more than one supercharging device may be used at the same engine.
JP published patent application No 2000-230427 refers to an internal combustion engine with a supercharger, which via a clutch adapted to connect and disconnect the engine and the supercharger.
WO 2004/025097 A1 discloses a method for operating an internal combustion engine having a turbocharger with a separate compressor driven via a belt-drive from the engine crankshaft, said compressor being connected to the inlet of the turbocharger for increasing the pressure of the intake air delivered to the turbocharger This means that the losses increase due to additional pressurized conduits between the separate compressor and the turbocharger, and also increased mechanical compressor losses at high motor speeds.